Aluminum flakes are used in broad fields as a metallic pigment contained in paint compositions, ink compositions, resin compositions, cosmetics and the like.
In general, aluminum flakes are obtained by wet-grinding an aluminum powder as a raw material (also referred to as “raw material aluminum powder”) and a grinding aid in an organic solvent by using a grinding device having grinding media such as a ball mill or an attritor to flake the aluminum powder as a raw material.
The metallic texture of a paint film obtained by applying a paint or the like containing aluminum flakes to a base material is determined principally by the shape, the surface smoothness, the average particle size, the particle size distribution, the average thickness, the thickness distribution, the aspect ratio and so on of the aluminum flakes, and these parameters are adjusted by the combination of the properties of the raw material aluminum powder and the grinding condition. WO 2003/022934 (hereinafter, Patent Document 1) discloses development of a technique of obtaining an aluminum flake pigment having high brightness by adjusting these parameters.